Photographic diffusion-transfer processes and elements utilizing ph-sensitive optical filter agents to prevent fogging by extraneous actinic radiation during development

ABSTRACT

THIS INVENTION RELATES TO PHOTOGRAPHY, AND MORE PARTICULARLY, IT RELATES TO THE USE OF CERTAIN INDICATOR DYES DERIVED FROM PHENOLS AS OPTICAL FILTER AGENTS TO PROTECT A SELECTIVELY EXPOSED PHOTOSENSITIVE MATERIAL FROM POSTEXPOSURE FOGGING IN PHOTOGRAPHIC PROCESSES WHERE DEVELOPMENT OF THE PHOTOSENSITIVE MATERIAL IS CONDUCTED IN THE PRESENCE OF EXTRANEOUS INDIDENT LIGHT. THIS CLASS OF PHENOL INDICATOR DYES CONTAIN A RING-CLOSING MOIETY BONDED TO TWO HYDROXY-SUBSTITUTED CARBOCYCLIC ARYL RADICALS SELECTED FROM TWO P-HYDROXYPHENYL RADICALS EACH POSSESSING A HYDROGEN-BONDING GROUP ADJACENT TO THE P-HYDROXY GROUP AND TWO P-PHYDROXYNAPHTHYL RADICALS AT LEAST ONE OF THE P-HYDROXYNAPHTYL RADICALS POSSESSING A HYDROGENBONDING GROUP ADJACENT TO THE P-HYDROXY GROUP. AT A FIRST PH IN ALKALINE SOLUTION THEY HAVE A HIGHLY COLORED, LIGHTABSORBING FORM CAPABLE OF ABSORBING RADIATION WITHIN A PREDETERMINED WAVELENGTH RANGE IN THE LONGER WAVELENGTH REGION OF THE VISIBLE SPECTRUM AND AT A SECOND LESS ALKALINE PH HAVE A COLORLESS FORM THAT IS SUBSTANTIALLY NON-LIGHTABSORBING IN THE VISIBLE SPECTRUM. BY SELECTING A DYE FROM THIS CLASS WHICH IS IN ITS LIGHT-ASBORBING FORM AT THE PH AT WHICH DEVELOPMENT IS PREFORMED, PROTECTION OF THE EXPOSED PHOTOSENSITIVE MATERIAL FROM RADIATION ACTINIC THERETO IS AFFORDED WITHIN THE WAVELENGTH RANGE ABSORBED BY THE DYE AND SUBSEQUENT TO AT LEAST THE INITIAL STAGES OF DEVELOPMENT, THE DYE MAY BE RENDERED SUBSTANTIALLY COLORLESS BY ADJSTING THE PH TO PERMIT VIEWING OF THE FINAL IMAGE. IN A PREFERRED EMBODIMENT, THE PHENOL DYE OR DYES ARE USED IN CONJUNCTION WITH A SECOND DYE OR DYES HAVING A PRINCIPAL ABSORPTION IN AT LEAST A PARTIALLY DIFFERENT WAVELENGTH RANGE, AND THE PHENOL DYE(S) AND SECOND DYE(S) TOGETHER AFFORD PROTECTION OVER THE WAVELENGTH RANGE OF ABOUT 400 MM. TO 700 MM.

M S. SIMON ETAL PHOTOGRAPHIC DIFFUSION-TEANSFER PROCESSES ANl) ELEMENTS UTLLIZING H-SENSITIVE OPTICAL FILTER AGENTS TO PREVENT FOGGING BY EXTRANEOUS ACTINIC RADIATION DURING DEVELOPMENT Filed. Jan. 4, 1971 l0 Sheets-Sheet l INVENTORS MvRorx s SIMON 0 BY DAVID e WALLER @lcownwwlwwa ATTORNEYS NOV. 7, 1972 5, SIMON ETAL 3,7QZZ45 PHOTOGRAPHIC DIFFUSION-TRANSFER PROCESSES AND ELEMENTS UTILIZING H-SENSITIVE OPTICAL. FILTER AGENTS TO PREVENT FOGGING BY EXTRANEOUS ACTINIC RADIATION DURING DEVELOPMENT Filed Jan. 4, 1971 10 Sheets-Sheet 2 INVENTORS MYROm S. SIMON BY DAVID R WALLER AT TORNE YS New? 1972 SIMON ETAL 3,7@2,245

PHOTOGRAPHIC DIFFUSION-TRANSFER PROCESSES AND ELEMENTS UTILIZING pH-SENSITIVE OPTICAL FILTER AGENTS To PREVENT FOGGING BY EXTRANEOUS ACTINIC RADIATION DURING DEVELOPMENT Filed Jan. 4, 1971 10 Sheets-Sheet 3 INVENTORS MYRON S. SIMON and DAVID P WALLER ATTORNEYS Nov. 7, 1972 3 m; EI'AL 3,702,245

PHOTOGRAPHIC DIFFUSION-TRANSFER PROCESSES AND ELEMENTS UTILIZING PH-SENSITIVE OPTICAL FILTER AGENTS To PREVENT FOGGING BY EXTRANEOUS ACTINIC RADIATION DURING DEVELOPMENT Filed Jan. 4, 1971 10 Sheets-Sheet 4,

INVENTORS MYRON S. SIMON an DAVlD P WALLER ATTORNEYS PHOTOGRAPH I0 DIFFUSION-TRANSFER PROCESSES AND ELEMENTS UTILIZING pH-SENSITIVE OPTICAL FILTER AGENTS TO PREVENT FOGGING BY EXTRANEOUS ACTINIC RADIATION DURING DEVELOPMENT Filed Jan. 4, 1971 10 Sheets-Sheet 5 m 2 g o E Q E .J i 2 w 55 0 (3 o 5 8 9 LL 4 3 o LO Q o I IO b r :6 v I m m o '1 a; f 2 o o o o 0 8 (B'IVOS 90-1) ALISNHG NOISSIWSNVELL 'IVOLLdO INVENTORS MYRON SIMON on By DAVID P. WALLER filcow n a/nd We ATTORNEYS 1972 M. s. SIMON ETAL 3,7022

PHOTOGRAPHIC DIFFUSION-TRANSFER PROCESSES AND ELEMENTS UTILIZING pH-SENSITIVE OPTICAL FILTER AGENTS To PREVENT FOGGING BY EXTRANEOUS ACTINIC RADIATION DURING DEVELOPMENT Filed Jan. 4, 1971 10 sheets -Sheet 6 IN MILLIMICRONS WAVE LENGTH 9 o d O a-wos eo-n ALISNZIO NOISSIWSNVHL IVOLLdO INVENTORS MYRo s. SIMON BY DAVID P. WALLER @MM amd mm ATTORNEYS NOV. 7, 1972 s o EIAL 3,7Q2,24 PHOTOGRAPHIC DIFFUSION-TRANSFER PROCESSES AND ELEMENTS UTILIZING pH-SENSITIVE OPTICAL FILTER AGENTS TO PREVENT FOGGING BY EXTRANEOUS ACTINIC RADIATION DURING DEVELOPMENT Filed Jan. 4, 1971 lo Sheets-Sheet 7 u) Q 2 8 8 Q g .1 O E 2 Q I u-n U 3: g

o I I m I ,5 lb o m 3 '2 9 0 0 O o o 8 (Twas 90") LLISNBU NOISSIWS.. H.L 'TVQLLdO- ENTORS MYRON SIMON ("I By DAVID I? WALLER ATTORNEYS NOV. 7, 1972 5, SIMON EI'AL 3,7Q2,4 PHOTOGRAPHIC DIFFUSION-TRANSFER PROCESSES AND ELEMENTS UTILIZING pH-SENSITIVE OPTICAL FILTER AGENTS TO PREVENT FOGGING BY EXTRANEOUS ACTINIC RADIATION DURING DEVELOPMENT Filed Jan. 4, 1971 10 Sheets-Sheet 8 (H'IVQS 901) ALISNBCI NOISSIWSNVHJ. 'IVOLLdO INVENTORS MYRON S. SIMON and BY DAVID R WALLER E/ww n amal m ATTORNEYS NOV. 7, 1972 5, SIMON EI'AL PHOTOGRAPHIC DIFFUSION-TRANSFER PROCESSES AND ELEMENTS UTILIZING pH-SENSITIVE OPTICAL FILTER AGENTS TO PREVENT FOGGING BY EXTRANEOUS ACTINIC RADIATION DURING DEVELOPMENT Filed Jan. 4, 1971 10 Sheets-Sheet 9 Omw OON

Mimi

r Nd mQO (B'WOS 90'!) AllSNBG NOISSIWSNVHJ. 'IVOLLdO INVENTORS MYRON S. SIMON an DAVID E WALLER ATTORNEYS 1972 M. s. SIMON ETAL 3,702,25

PHOTOGRAPHIC DIFFUSION-TRANSFER PROCESSES AND ELEMENTS UTILIZING pH-SENSITIVE OPTICAL FILTER AGENTS TO PREVENT FOGGING BY EXTRANEOUS ACTINIC RADIATION DURING DEVELOPMENT Filed Jan. 4, 1971 10 Sheets-Sheet 10 550 WAVELENGTH IN MILLIMICRONS FIG. I3

BY DAVID E WALLER 26W M 1m ATTORNEYS United States Patent Office 3,702,245 Patented Nov. 7, 1972 3,702,245 PHOTOGRAPHIC DIFFUSION-TRANSFER PROC- ESSES AND ELEMENTS UTILIZING pH-SENSI- TIVE OPTICAL FILTER AGENTS TO PREVENT FOGGING BY EXTRANEOUS ACTINIC RADIA- TION DURING DEVELOPMENT Myron S. Simon, West Newton, and David P. Waller, Arlington, Mass, assignors to Polaroid Corporation, Cambridge, Mass.

Filed Jan. 4, 1971, Ser. No. 103,392 Int. Cl. G03c 5/54, 7/00, 1/40 US. Cl. 96-3 103 Claims ABSTRACT OF THE DISCLOSURE This invention relates to photography, and more particularly, it relates to the use of certain indicator dyes derived from phenols as optical filter agents to protect a selectively exposed photosensitive material from postexposure fogging in photographic processes where development of the photosensitive material is conducted in the presence of extraneous incident light. This class of phenol indicator dyes contain a ring-closing moiety bonded to two hydroxy-substituted carbocyclic aryl radicals selected from two p-hydroxyphenyl radicals each possessing a hydrogen-bonding group adjacent to the p-hydroxy group and two p-hydroxynaphthyl radicals at least one of the p-hydroxynaphthyl radicals possessing a hydrogenbonding group adjacent to the p-hydroxy group. At a first pH in alkaline solution they have a highly colored, lightabsorbing form capable of absorbing radiation within a predetermined wavelength range in the longer wavelength region of the visible spectrum and at a second less alkaline pH have a colorless form that is substantially non-lightabsorbing in the visible spectrum. By selecting a dye from this class which is in its light-absorbing form at the pH at which development is performed, protection of the exposed photosensitive material from radiation actinic thereto is afforded within the wavelength range absorbed by the dye and subsequent to at least the initial stages of development, the dye may be rendered substantially colorless by adjsting the pH to permit viewing of the final image.

In a preferred embodiment, the phenol dye or dyes are used in conjunction with a second dye or dyes having a principal absorption in at least a partially different wavelength range, and the phenol dye(s) and second dye(s) together afford protection over the wavelength range of about 400 nm. to 700 nm.

BACKGROUND OF THE INVENTION (1) Field of the invention The present invention relates to photography and more particularly to photographic processes and products wherein light-absorbing dyes are employed as optical filter agents to protect a selectively exposed photosensitive material from further exposure by incident radiation actinic thereto during processing in the presence of light.

(2) Description of the prior art The production of both silver and color images including monochromatic and multicolor images employing diffusion transfer techniques is now well-known. In these processes, a photosensitive element comprising a layer of photosensitive material is exposed to provide a latent image therein and wetted by a liquid processing composition, for example, by immersion, coating, spraying, flowing, etc., in the dark, and the exposed photosensitive element superposed prior to, during or after wetting, on a sheetlike support element which may be utilized as an image-receiving element. As a function of developing the latent image, there is formed an imagewise distribution of image-forming components which imagewise distribution is transferred, by imbibition, to form the final image either in the photosensitive or image-receiving element.

US. Pat. No. 3,415,644, discloses a composite photosensitive structure, particularly adapted for use in reflection type photographic diffusion transfer color processes. This structure comprises a plurality of essential layers including, in sequence, a dimensionally stable opaque layer; one or more silver halide emulsion layers having associated therewith dye image-providing material which is soluble and diffusible, in alkali, at a first pH, as a function of the point-to-point degree of its associated silver halide emulsions exposure to incident actinic radiation; a polymeric layer adapted to receive solubilized dye image-providing material diffusing thereto; a polymeric layer containing suflicient acidifying capacity to effect reduction of a processing composition from the first pH to a second pH at which the dye image-providing material is substantially nondiflusible; and a dimensionally stable transparent layer. This structure may be exposed to incident actinic radiation and processed by interposing, intermediate the silver halide emulsion layer and the reception layer, an alkaline processing composition providing the first pH and containing a light-reflecting agent, for example, titanium dioxide to provide a white background. The light-reflecting agent (referred to in said patent as an opacifying agent) also performs an opacifying function, i e., it is effective to mask the developed silver halide emulsions and also acts to protect the photoexposed emulsions from postexposure fogging by light passing through the transparent layer if the photo-exposed film unit is removed from the camera before image formation is complete.

In a preferred embodiment, the composite photosensitive structure includes a rupturable container, retaining the alkaline processing composition having the first pH and reflecting agent, fixedly positioned extending transverse a leading edge of the composite structure in order to effect, upon application of compressive pressure to the container, discharge of the processing composition intermediate the opposed surfaces of the reception layer and the next adjacent silver halide emulsion.

The liquid processing composition distributed intermediate the reception layer and the silver halide emulsion, permeates the silver halide emulsion layers of the composite photosensitive structure to initiate development of the latent images contained therein resultant from photoexposure. As a consequence of the development of the latent images, dye image-providing material associated with each of the respective silver halide emulsion layers is individually immobilized as a function of the point-topoint degree of the respective silver halide emulsion layer photoexposure, resulting in imagewise distributions of mobile dye image-providing materials adapted to transfer, by diffusion, to the reception layer to provide the desired transfer dye image. Subsequent to substantial dye image formation in the reception layer, a sufficient portion of the ions of the alkaline processing composition transfers, by diffusion, to the polymeric neutralizing layer to effect reduction in the alkalinity of the composite film unit to the second pH at which dye image-providing material is substantially non-dilfusible, and further dye image-providing material transfer is thereby substantially obviated.

The transfer dye image is viewed, as a reflection image, through the dimensionally stable transparent layer against the background provided by the reflecting agent, distributed as a component of the processing composition, intermediate the reception layer and next adjacent silver halide emulsion layer. The thus-formed stratum effectively masks residual dye image-providing material retained in association with the developed silver halide emulsion layer subsequent to processing.

In the copending U.S. patent application Ser. No. 786,352 of Edwin H. Land, filed Dec. 23, 1968, now abandoned, and copending -U.S. patent application Ser. No. 101,968 filed Dec. 28, 1970, in part a continuation of Ser. No. 786,352, an organic light-absorbing reagent (or optical filter agent), such as a dye, which is present as a light-absorbing species at the first pH and which may be converted to a substantially non-light-absorbing species at the second pH is used in conjunction with the light-reflecting agent to protect the selectively exposed silver halide emulsions from post-exposure fogging when development of the photoexposed emulsions is conducted in the presence of extraneous incident actinic radiation impinging on the transparent layer of the film unit.

In the copending US. patent application Ser. No. 43,782, of Edwin H. Land, filed June 5, 1970, now abandoned, the stratum interposed intermediate, the reception layer and next adjacent silver halide layer is disclosed to comprise an inorganic light-reflecting pigment dispersion containing reflecting pigment in a concentration per se insufficient, distributed as a layer intermediate the reception layer and next adjacent silver halide layer, to effectively prevent transmission of a given level of radiation actinic to the silver halide layer therethrough and at least one optical filter agent at a pH above the pKa of the optical filter agent, in a concentration per se also insufficient to prevent transmission of said given level of actinic radiation therethrough, which concentrations individually and additively are together insufficient to prevent said transmission of incident actinic radiation but in admixture are synergistically effective to provide the requisite transmission density to prevent such transmission of said given level of radiation until modulation of the environmental pH to below the pKa of the optical filter agent whereby the transmission density is rendered sufficiently low to permit substantially immediate viewing of transfer image formation against the background provided by the refiecting pigment.

SUMMARY OF THE INVENTION It is the primary object of the present invention to provide photographic processes, products and compositions, employing as optical filter agents, a particular class of indicator dyes derived from certain hydroxy-substituted carbocyclic aryl compounds, specifically, certain phenol compounds.

Other objects of the present invention will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises the processes involving the several steps and the relation and order of one or more of such steps with respect to each of the others, and the products and compositions possessing the features, properties and the relation of elements which are exemplified in the following detailed disclosure, and the scope of the application of which will be indicated in the claims.

According to the present invention, it has been found that certain dyes, namely, indicator dyes derived from certain phenols and benzphenols, i.e., naphthols are eminently suitable for use as optical filter agents for protecting an exposed photosensitive material from postexposure fogging in photographic processes where the photosensitive material subsequent to selective exposure to form a latent image therein and during at least the initial stages of developing the latent image, is non-selectively exposed to extraneous incident light. This class of phenol indicator dyes as will be defined more particularly hereinafter contain a ring-closing moiety bonded to two hydroxy-substituted carbocyclic aryl radicals selected from two p-hydroxyphenyl radicals each possessing a hydrogenbonding group adjacent to the p-hydroxy group and two p-hydroxynaphthyl radicals at least one of the p-hydroxynaphthly radicals possessing a hydrogen-bonding group adjacent to the p-hydroxy group.

Like pH sensitive dyes in general, these phenol indicator dyes possess spectral absorption characteristics which are reversibly alterable in response to changes in environmental pH. These dyes possess a highly colored form capable of absorbing visible radiation in alkaline media at a first pH value above their respective pKa and a substantially colorless form, i.e., a form which is substantially non-light-absorbing in the visible spectrum in less alkaline media at a second pH value below their respective pKa. By pKa is meant the pH at which about 50% of the dye is present in its light-absorbing form and about 50% is present in its non-light-absorbing form.

In addition to their color-changing properties, these dyes possess certain other characteristics that render them especially suitable for photographic use. The phenol dyes described above possess a pKa such that they are useful in many commercial photographic processes conducted under alkaline conditions, and dyes may be selected from this class for use in conventional tray processes and for use in diffusion transfer and other processes where development is performed at a relatively high pH. In their colored form, they are capable of absorbing radiation in the longer wavelength region of the visible spectrum, and depending upon the particular dye selected afford protection of photographic materials from post-exposure fogging substantially throughout the green and red portions of the spectrum. To achieve a highly effective light absorbing system throughout the visible spectrum, i.e., between about 400 nm. and 700 nm., the aforementioned class of phenol dyes may be used in combination with another optical filter agent, such as a second dye or dyes, which are effective absorbers of radiation in the shorter wavelength, i.e., blue region of the spectrum.

Because of their pKa and spectral absorption characteristics coupled with their ability to be rendered alternately light-absorbing and non-light-absorbing by adjusting the pH of their environment, the above-denoted class of phenol dyes finds particular utility in photographic processes employing composite photographic film units containing means for modulating environmental pH, and particularly, in diffusion transfer processes of the type described in aforementioned US. Pat. No. 3,415,644 and in aforementioned US. patent applications Ser. Nos. 786,- 352; 43,782 and 101,968. For convenience, the specifications of these applications and of the patent are specifically incorporated herein.

Specifically, the present invention is directed to photographic processes comprising the steps of selectively exposing a photosensitive element comprising a layer of photosensitive material to radiation actinic thereto to provide a latent image therein, applying a processing composition to provide a phenol indicator dye of the abovedenoted class in a form capable of absorbing a predetermined wavelength range of said radiation actinic to said photosensitive material, and developing said latent image while exposing said photosensitive element non-selectively to incident actinic radiation within said predetermined wavelength range, said indicator dye being present during development in a position and quantity effective to absorb radiation within said wavelength range of incident radiation in an amount sufiicient to prevent any substantial increase in the minimum density of the image obtained by said development of said latent image.

In another embodiment, a second dye(s) is present which has a principal absorption in a second and at least partly different predetermined wavelength range and the phenol dye(s) and said second dye(s) together absorb radiation over the range of 400 nm. to 700 nm.

In a further embodiment, the second dye(s) is also an indicator dye having spectral absorption characteristics reversibly alterable in response to the pH of its environment, and the phenol dye(s) and second dye(s) are converted to a substantially non-light absorbing form subsequent to at least the initial stages of development of the latent image.

In a preferred embodiment, the second dye or dyes used in conjunction with the phenol indicator dyes are indicator dyes derived from indoles.

The photographic products provided by the present invention comprise a support layer carrying a layer of photosensitive material having associated therewith a phenol indicator dye of the above-denoted class.

In another embodiment, the photographic products are photographic film units particularly adapted for production of a transfer image by diffusion transfer processes and may be constructed to include a photosensitive element containing a layer of photosensitive material and an optical filter agent of the above-denoted class of phenol indicator dyes adapted, subsequent to selective exposure of the photosensitive layer to form a latent image therein, to selectively absorb incident actinic radiation without deleteriously affecting either the composition of and/or the development of the latent image, and a diffusion transfer image-receiving element.

In a further embodiment of the present invention, the photographic products are film units specifically adapted to provide a dye transfer image by color diffusion transfer processes. The photosensitive layer, e.g., a photosensitive silver halide layer will have associated therewith a compound providing, as a function of development of a latent image in the associated silver halide layer, an imagewise distribution of a dye image-forming material which is soluble and diffusible in the processing composition, and an optical filter agent of the above-denoted class of phenol indicator dyes adapted, as a function of environmental pH to selectively effect absorption ofincident actinic radiation, subsequent to selective exposure of the photosensitive layer to form the latent image therein.

In a preferred embodiment of the present invention, a second pH sensitive dye or dyes preferably, an indole indicator dye will be used in conjunction with the abovedenoted phenol indicator dyes, which dyes together will absorb incident actinic radiation over the wavelength range of 400 nm. to 700 run. The film unit employed will comprise a composite photosensitive element including, in sequence, a first layer or support material, two or more photosensitive silver halide layers each having associated therewith a compound providing, as a function of development of a latent image in the associated silver halide layer, an imagewise distribution of image-forming material which is soluble and difiusible in the processing composition, a layer adapted to receive image-forming material diffusing thereto, a second layer or support material and means for modulating the pH of the film unit. In combination with the composite structure, a rupturable container retaining a processing composition is fixedly positioned and extends transverse a leading edge of the composite structure whereby to effect, upon application of compressive pressure, discharge of the processing composition intermediate the image-receiving layer and the next adjacent photosensitive silver halide layer.

For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a photographic film unit embodying the invention;

FIGS. 2, 4 and 6 are diagrammatic enlarged cross-sectional views of the film unit of FIG. 1, along section line 22, illustrating the association of elements during the the three illustrated states of the performance of a diffusion transfer process, for the production of a multicolor transfer image according to the invention, the thickness of the various materials being exaggerated, and wherein FIG. 2 represents an exposure stage, FIG. 4 represents a processing stage and FIG. 6 represents a product of the process;

FIGS. 3, 5 and 7 are diagrammatic, further enlarged cross-sectional views of the film unit of FIGS. 2, 4 and -6, along sections lines 33, 55 and 77, respectively, further illustrating, in detail, the arrangement of layers comprising the photosensitive laminate during the three illustrated stages of the transfer process; and

FIGS. 8 to 13 are graphic illustrations of the spectral absortpion characteristics of indicator dyes of the present invention designated hereinafter as otpical filter agents B and C through G representing the optical transmission density, i.e., absorbance of the respective agents measurel on a logarithm scale over the wavelength range of 350 nm. to 750 nm. in aqueous alkaline solution at a pH substantially above their pKa.

DETAILED DESCRIPTION OF THE INVENTION As noted above, it has been found in accordance with the present invention that a selectively exposed photosensitive material having a latent image therein may be processed in the presence of extraneous incident radiation actinic thereto within the longer wavelength region of the visible spectrum by reason of the protection afforded by a particular class of indicator dyes derived from certain phenols. Such dyes may be represented by the formula:

wherein A and B are selected from a first and second phydroxyphenyl radical each possessing a hydrogen-bonding group adjacent to the p-hydroxy group and a first and second p-hydroxynaphthyl radical, at least one of said phydroxynaphthyl radicals possessing a hydrogen-bonding group adjacent to the p-hydroxy group and X represents the atoms necessary to complete a ring-closing moiety.

In the above formula, any hydrogen-bonding group may be used that is capable of raising the pKa. The association of two atoms through hydrogen to form a hydrogen bond between or within molecules is well known. When hydrogen is attached to an electronegative atom, for example 0 or N, the resultant bond is polarized. If directed toward another atom (M) with an unshared pair of electrons, the hydrogen acts as a bridge between the atoms (0-H M) due to the eletcrostatic attraction to both atoms between which the hydrogen proton can be transferred. In the present invention an intramolecular hydrogen bond is formed between the p-hydroxy group and an adjacent hydrogen-bonding group, i.e., a group containing a heteroatom possessing an active unshared pair of electrons, such as O, N, S or haolgen, e.g., F which has a free electron pair or negative charge in basic solution and which is capable of forming a 5-, 6- or 7-membered and preferably a 5- or 6-membered hydrogenbonded ring with the p-hydroxy group. Preferably, the heteroatom in the hydrogen-bonding group has attached to it a proton which is more acidic than the proton on the phenolic or naphtholic -OH and ionizes in basic solution to a negative charge. Such groups include, for example, carboxy; hydroxy; o-hydroxyphenyl; bis trifiuoromethyl carbinol; sulfonamido (-NH-SO R wherein R may be alkyl, aryl, alkaryl); and sulfamoyl (SO --NH*R' wherein R; may be alkyl, aryl, 'alkaryl) Suitable R and and R substituents include branched or straight chain alkyl, e.g., methyl, ethyl, isopropyl, n-butyl, t-butyl, hexyl, octyl, dodecyl, hexadecyl, octadecyl and eicosanyl; aryl, e.g., phenyl and naphthyl; and alkaryl, e.g. benzyl, phenethyl, phenylhexyl, p-octylphenyl and pdodecylphenyl.

Where it is desired that the indicator dye be substantially immobile or non-ditfusible in the processing solution,

compounds containing a sulfamoyl or sulfonamido substituent afford the distinct advantage of allowing the immobilizing function to be combined with the hydrogen bonding function by selecting sulfonamido (NHSO --R) or sulfamoyl (SO NH-R') groups containing as R or R an immobilizing group, such as, hexadecyl or pdodecylphenyl.

The ring-closing moiety may be any of those commonly used in pH sensitive dyes, such as, a phenolate, carboxylate or sulfonate, and preferably is a phenolate, such as, 3,4-benzochromane or a carboxylate such as a phthalide or naphthalide.

The compounds represented in the above formula may contain substituents other than those specified. Besides the hydrogen-bonding groups, the A and/or B radicals and/or the ring-closing moiety may be substituted, for example, With solubilizing groups to enhance the solubility of the indicator dye in the particular processing composition employed; with immobilizing groups Where it is desired to render the indicator dye substantially nondiffusi-ble in the processing composition; with additional hydrogen-bonding or other groups as appropriate to adjust the pKa of the indicator dye for the particular processing conditions employed; and with other substituents, such as alkyl groups, which do not interfere with the photographic function of the indicator dye as an optical filter agent. Typical substituents include branched or straight chain alkyl, such as methyl, ethyl, isopropyl, t-butyl, octayl, hexadecyl, and eicosanyl; aryl, such as, phenyl and naphthyl; alkaryl, such as, benzyl, phenethyl, phenylhexyl, and p-dodecylphenyl; alkoxy, such as, methoxy, ethoxy, butoxy, l-ethoxy-2-(fi-ethoxyethoxy) and octadecyloxy; aryloxy, such as phenoxy, benzyloxy and naphthoxy; alkoxyalkyl, such as methoxyethyl, ethoxyethoxyethyl and dodecyloxyethyl; halo, such as, fluoro, bromo and chloro; sulfo; carboxy; hydroxy; and amino including monoand disubstituted amino, e.g., N-alkylamino and N,N'-di-alkylamino. Such substitutents may be substituted on the A and/or B radical and/or on the ring-closing moiety.

In addition to the above, the hydrogen-bonding or other substituent may comprise a fused ring. For example, the A and/or B radical may contain as a substituent, a cycloaliphatic or an aromatic ring usually having 5 or 6 members, carbocyclic or heterocyclic and substituted or unsubstituted, bonded to adjacent carbon atoms, e.g.,

and

Where selective exposure of the photosensitive material is made through a layer containing the indicator dye, then the dyes should be in a non-light-absorbing form until the processing solution is applied. Alternately, the dyes may be initially disposed in the processing composition in their light-absorbing form, for example, in the developing bath in tray processing or in the layer of processing solution distributed between the photosensitive element and the superposed image-receiving element (or spreader sheet) in diffusion transfer processing. The particular indicator dye or dyes selected should have an absorption spectrum corresponding to the sensitivity of the photosensitive layer, so as to afford protection over the predetermined wavelength range required by the particular photosensitive material employed and should have a pKa such that they are in their colored form, i.e., light-absorbing form at the pH at which the photographic process is performed. Most commercially useful photographic processes are performed under alkaline conditions. Diffusion transfer processes, for example, usually employ highly alkaline processing solutions having a pH in excess of 12. Accordingly, a dye or dyes will be selected from the above-denoted class which will have the appropriate pKa for the particular processing conditions employed.

In photographic processes where the optical filter agent is retained in a stratum through which the final image is to be viewed, the color of the indicator dye may be discharged subsequent to image formation by reducing the environmental pH of the system to a value at Which the dye is substantially non-light-a'bsorbing in the visible spectrum. In processes where the optical filter agent is removed or separated from the layer containing the final image or retained in a layer that does not interfere with viewing of the final image, it is unnecessary to convert the indicator dye to its non-light-absorbing form, though the color may be discharged if desired.

The concentration of indicator dye is selected to provide the optical transmission density required, in combination with other layers intermediate the silver halide emulsion layer(s) and the incident radiation, to prevent nonimagewise exposure, i.e., fogging, by incident actinic light during the performance of the particular photographic process. It has been found, by interposing neutral density (carbon containing) filters over a layer of titanium dioxide, that a transmission density of approximately 6.0 from said neutral density filters was effective to prevent fogging of a diffusion transfer multicolor film unit of the type described in said US. Patent No. 3,415,644 having a transparent support layer and an Equivalent ASA Exposure Index of approximately 75 When processed for one minute in 10,000 foot candles of color corrected light, a light intensity approximating the intensity of a noon summer sun. The transmission density required to protect such a film unit under the stated conditions may also be expressed in terms of the system transmission density of all the layers intermediate the silver halide layer(s) and the incident light; the system transmission density required to protect color film units of the aforementioned type and photographic speed has been found to be on the order of 7.0 to 7.2. Lesser levels of optical transmission density would, of course, provide effective protection for shorter processing times, lesser light intensities and/or films having lower exposure indices. The transmission density and the indicator dye concentration necessary to provide one requisite protection from incident light may be readily determined for any photographic process by following the above described procedure or obvious modi fications thereof.

Since most commercial photographic processes employ photosensitive materials sensitive to and exposable by actinic radiation throughout the visible spectrum, e.g., blackand-white panchromatic silver halide emulsions and rnultilayer silver halide emulsion elements, it is preferred to use a second dye in conjunction with the phenol dye that has a principal absorption in a second and at least partially different predetermined wavelength range such that the combination of dyes will afford protection from nonselective incident actinic radiation over the range of 400 to 700 nm. The second dye employed may be non-colorchanging but preferably, is also pH sensitive, i.e., has reversibly alterable spectral absorption characteristics in response to changes in the environmental pH so that it may be rendered light-absorbing or non-light-absorbing as desired. Illustrative of such dyes are indicators, derived from indoles. The second dye also may be initially present in the film unit or in the processing composition as discussed above either together with or separate from the phenol dye, and subsequent to processing may be removed from the film unit or retained within the film structure, provided it is in a form or position such that it does not interfere with viewing of the image produced.

As noted above, in its preferred embodiment, the present invention is concerned with composite diffusion transfer photosensitive elements including a film pack or roll wherein superposed photosensitive and image-receiving elements are maintained as a laminate after formation of the final image. Such elements include at least one transparent support to allow viewing of the final image without destroying the structural integrity of the film unit. Preferably, the support carrying the photosensitive layer(s) is opaque and the support carrying the imagereceiving layer is transparent and selective photoexposure of the photosenstive layer(s) and viewing of the final image both are effected through the latter support. The final image is viewed as a reflection print, i.e., by reflected light, provided by a reflecting agent initially disposed in the processing composition applied and maintained intermediate the irnage-receiving and next adjacent photosensitive layer or by a preformed layer of reflecting agent initially positioned intermediate the image-receiving and next adjacent photosensitive layer. It will be understood that a preformed reflecting layer, while it should be capable of masking the photosensitive layer(s) subsequent to image formation, should not interfere with selective photoexposure of the photosensitive material prior to processing.

When utilizing reflection-type composite film units, the indicator dye or dyes employed as the optical filter agent(s) may be positioned initially in a layer of the film unit, e.g., in a layer between the image-receiving and next adjacent photosensitive layer through which photoexposure is effected provided it is incorporated under conditions, i.e., at a pH such that it will not absorb actinic radiation intended to selectively expose the photosensitive material to form a latent image therein. For example, the optical filter agent may be in a layer coated over either the image-receiving layer or the next adjacent photosensitive layer and should remain substantially nonlight-absorbing until a processing composition is applied providing a pH at which the indicator dye is capable of being rapidly converted to its light-absorbing form to provide light protection when the film unit is removed from the camera. Rather than being initially disposed in the film unit, the indicator dye may be initially present in the processing composition applied intermediate the image-receiving and next adjacent photosensitive layer subsequent to photoexposure. The dye, when initially disposed in the processing composition, will be in its light-absorbing form.

Subsequent to processing, the indicator dye selected as the optical filter agent should be in a form or in a position such that it does not interfere with viewing of the image produced. This result may be achieved in various ways, for example, by hiding the optical filter agent behind the reflecting layer used to mask the photosensitive layer(s) and to provide a background for viewing the final image through the transparent receiving element. As noted above, however, the phenol dyes of the abovedenoted class may be rendered substantially colorless by reducing the environmental pH and thus, are especially useful in composite photosensitive elements were the dye selected is preferably one that is readily converted to its non-light absorbing form subsequent to substantial image formtaion as the pH of the film unit is adjusted to the final value desired for stabilizing the photographic system. Since the filter agent is rendered substantially nonlight-absorbing in the visible spectrum, its final position in the film unit does not have to be behind the reflecting layer. It may be in front of the reflecting layer and/ or in the reflecting layer itself, provided that if the indicator dye is associated with the final image, it will not have an adverse eflect on the stability of the image.

For use in diffusion transfer processes and other photographic processes employing highly alkaline processing solutions, it is desirable that the indicator dye selected as the optical filter agent possess a relatively high pKa so that the dye will be in a light-absorbing form during hte initial stages of processing and yet may be rendered substantially non-light absorbing within a relatively brief interval as the pH subsequent to substantial image formation is reduced. As noted above, in diffusion transfer processes employing reflection-type composite photosensitive elements, the indicator dyes used as the optical filter agents may be initially disposed in a layer of the film unit but preferably are initially disposed in the processing composition applied subsequent to selective photoexposure of the photosensitive structure. When incorporated into the processing composition, it is desirable that the dyes selected exhibit good stability in highly alkaline media in addition to effective absorption in the visible spectrum and a high pKa. Also, the dyes employed as optical filter agents are preferably substantially non-diffusible in the alkaline processing composition in order to achieve optimum efficiency as a radiation filter and to prevent diffusion of filter agent into layers of the film unit where its presence may be undesirable.

In accordance with the present invention, indicator dyes are provided which possess these characteristics in combination, namely, (1) efficient absorption of actinic radiation within the wavelength range of about 500 nm. to 700 nm., (2) a high pKa of 11 or more, (3) stability in highly alkaline media, and optionally, (4) non-ditfusibility in aqueous alkali. Such dyes may be represented by the following formulae:

wherein R is a hydrogen-bonding group having a negative charge in basic solution and X represents the atoms necessary to complete a ring-closing moiety selected from a naphthalide and a phthalide substituted with a carboxy group in at least one of the 4- and 7-positions.

The respective naphthalide and carboxyphthalide ringclosing moieties are illustrated below:

1 1 wherein at least one of R and R is a carboxy group.

(311 (Hi (III) wherein R and R the same or different, are hydrogenbonding groups having a negative charge in basic solution and X" represents the atoms necessary to complete a ringclosing moiety selected from a phthalide and a naphthalide.

As in Formula I, the dyes represented in Formulae II and III may contain additional substituents, as desired, which do not interfere with its photographic function as an optical filter agent such as solubilizing group(s), e.g., carboxy and sulfo groups and immobilizing gr0up(s), e. g., long chain alkyl groups or other bulky group either cyclic or acyclic which render the indicator dye substantially non-difiusible in the processing composition. As mentioned previously, rather than using a separate immobilizing group together with the hydrogen-bonding group, the immobilizing function may be combined with the hydrogenbonding function by selecting a group, such as, sulfonamido or sulfamoyl containing as R or R, a long chain alkyl or other bulky group. The additional substituents as may be selected for the compounds encompassed by Formulae II and III may be substituted on the phenol (or l-naphthol) radicals and/or on the ring-closing moiety.

Specific examples of indicator dyes useful as optical filter agents in accordance with the present invention include:

HO- OH HO OH (2) (3H OH HO OH CH3? /0 CHaO O (3) ('10 OH O O OH HO- OH I O CH: OCH:

011 $OOH COOH COOH

(46) O H OH l: 1 Lo 

